This invention relates to an optical transformation drawing apparatus in which an image is projected on to a rear face of a projection screen so that a draftsman can trace on the front face of the screen the image transmitted through the screen.
Many known apparatuses of this kind are stood non-adjustably on the ground or on a table, with the result that the draftsman is obliged to perform his work in a more or less bent-over posture.
There is a requirement for an optical transformation drawing apparatus which has the operating comfort of modern drawing apparatus, with which the draftsman can carry out his work either in a standing or in a sitting position. This requirement arises on the one hand due to the increase in the filming of drawings on microfilm, from which the draftsman is required to convert details, at the original scale of the drawing, into new drawings. On the other hand, a filming process is used for conversion of drawings to other scales, as for example in vehicle engineering and machine construction, or with an episcope for transforming charts or plans in the building industry. In these cases a distortion-free projected image up to the dimensions of DIN format A0 or a surface area of 1 square meter is desired.
Optical transformation drawing apparatuses of this size are expensive and heavy, as the optical system comprising a projection lamp, an image projection lens, an image holder, an objective lens and the projection screen forms a rigid unit and should not rock.
The expense is further increased if such a system is to be suspended so as to be pivotable so that the draftsman can adjust the inclination and height of the projection screen so as to enable him to work in a comfortable posture.